Various products such as disposable diapers, incontinence garments, sanitary napkins and the like include an absorbent fibrous pad as one component. This pad typically has a specific shape and is mass produced from a continuous fibrous web, which has been formed by air-laying fibrous material onto a foraminous forming substrate. Examples of this air-laying technique are described in U.S. Pat. Nos. 2,931,076, issued Apr. 5, 1960 to J. Clark; 3,886,629, issued June 3, 1975 to S. Nakai, et al.; 4,350,482, issued Sept. 21, 1982 to Alexandrov, et al.; and 3,906,588, issued Sept. 23, 1975 to D. Zafiroglu.
Various techniques have been employed to control the thickness or cross-directional profile of the air-layed fibrous web. For example, U.S. Pat. No. 3,748,693, issued July 31, 1973 to P. Jespersen employs a system of plates and moveable vanes to control the deposition of fibers on a foraminous conveyor. U.S. Pat. No. 4,375,448, issued Mar. 1, 1983 to D. Appel, et al. describes a method which provides a full-width feeding of dry fibers to a 2-dimensional flow control and fiber screening system. The system creates substantially no cross-flow forces, and ensures a uniform cross-directional basis weight profile. U.S. Pat. No. 4,375,447, issued Mar. 1, 1983 to R. Chung describes a method for pre-forming and feeding a lightly compacted batt of individualized fibers having a controlled cross-directional profile directly to a rotary fiber orienting and screening mechanism across the full width thereof. The method maintains a controlled cross-directional profile in an air-layed web of dry fibers.
To form a uniform air-layed fibrous web, a method and apparatus described in U.S. Pat. No. 4,285,647, issued Aug. 25, 1981 to C. Dunkerly, II employs a distributor and suction box which are cooperatively constructed and arranged to impart a velocity component to the fibers in the direction of movement of a forming wire. The angle of inclination of the fiber deposition relative to the moving forming wire ranges from about 21.degree.-30.degree.. U.S. Pat. No. 4,264,290, issued Apr. 28, 1981 to C. Dunkerly, II, et al. describes a device which has at least one air turning foil situated upstream from and at the level of the region between a fiber distributor and an underlying moving forming surface. Terminal edge portions of the foils direct ambient air in the direction of the forming surface movement to impart a uniform velocity component in the forming surface movement direction to fibers in transit between the distributor and the forming wire.
The following documents describe systems for blowing gaseously entrained fibers toward a forming surface to produce a nonwoven sheet material. U.S. Pat. No. 4,035,870, issued July 19, 1977 to I. Reba, et al. describes a depositing apparatus which employs a fiber transport means to direct gaseously entrained fibers through a bell former device at a high velocity toward a forming surface positioned adjacent to the outlet of the forming bell. U.S. Pat. No. 4,352,649, issued Oct. 5, 1982 to E. Jacobsen, et al. describes a system for producing nonwoven sheet material which includes compressed air nozzles arranged to force fiber material out of an outlet opening toward a forming surface.
Certain devices have employed stationary projections along an inner wall of a fiberizer and have employed directed gas streams to assist in the forming of individual fibers. For example, U.S. Pat. No. 3,268,954, issued Aug. 30, 1966 to C. Joa describes a device for disintegrating wood pulp board into component fibers and reassembling the fibers having a soft batt. The device disclosed by Joa includes a rotatable drum having an array of picking pins projecting therefrom. The device also has an array of stationary pins projecting toward the picking drum from a wall of a cylinder member that surrounds the drum. A series of air vents are arranged to force the leading ends of the pulp web toward the picking drum. U.S. Pat. No. 4,241,881, issued Dec. 30, 1980 to E. Laumer describes a fiberizer device which includes serrations formed along an interior surface of a hammermill. U.S. Pat. No. 3,918,126, issued Nov. 11, 1975 to D. Wood describes a fiberizer device which includes an air nozzle for directing pressurized air in a stream which strips textile fibers from the surface of a lickerin.
Other devices have employed masks or other types of air flow restricting devices positioned under a forming surface. For example, U.S. Pat. No. 3,973,291, issued Aug. 10, 1976 to C. Kolbach describes a device which employs a masking frame and a sequence of masks which prevent the establishment of partial vacuum through different predetermined sections of a pad-receiving compartment. The device forms discrete, shaped, profile pads.
U.S. Pat. No. 4,388,056 issued July 14, 1983 to F. B. Lee, et al. discloses another apparatus for continuously forming a cyclically contoured and densified air-laid fibrous web. The web has alternatively spaced narrow regions with relatively high basis weight and wide regions with relatively low basis weight. Adjustable shutter plates are configured to span a plurality of transverse plenum segments to modulate the air flow through the device.
Conventional fiberizing devices, such as those described above, have required very large volumes of pumped air to dilute and disperse the fibers, and significant amounts of energy have been required to pump these large volumes of air. The conventional devices have also required complicated mechanisms to form a contoured, profiled pad. For example, these devices have employed complex systems of masks and vanes to regulate the pressure drop across selected portions of a forming surface to thereby control the amount of fibers deposited on those selected portions. As a result, conventional fiberizing devices have been undesirably complicated and expensive to operate.